Sleep, Emotional and Behavioural Difficulties in Children and Adolescents

Alice M. Gregory

Department of Psychology, Goldsmiths, University of London and Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London, U.K. T: +44 (0)20 7919 7959; F: +44 (0)20 7919 7873; E:

Avi Sadeh

The Adler Center for Research in Child Development and Psychopathology, Department of Psychology, Tel Aviv University, Israel, T: +972 3-6409296;F: +972-3-6409547; E:

Running head: Sleep, emotional and behavioural problems in youth

For submission to: Sleep Medicine Reviews

Conflicts of interests: The authors declare no conflicts of interests.

Corresponding author: Alice Gregory

Sleep, Emotional and Behavioural Difficulties in Children and Adolescents

Abstract

Links between sleep and psychopathology are complex and likely bidirectional. Sleep problems and alteration of normal sleep patterns have been identified in major forms of child psychopathology including anxiety, depression and attention disorders as well as symptoms of difficulties in the full-range. This review summarizes some key findings with regards to the links between sleep and associated difficulties in childhood and adolescence. It then proposes a selection of possible mechanisms underlying some of these associations. Suggestions for future research include the need to 1) use multi-methods to assess sleep; 2) measure sleep in large-scale studies; 3) conduct controlled experiments to further establish the effects of sleep variations on emotional and behavioural difficulties; 4) take an interdisciplinary approach to further understand the links between sleep and associated difficulties.

Key words: Adolescent, Behavioural, Child, Emotional, Externalising, Internalising, Psychopathology

Abbreviations
Abbreviation / Full text
ADHD / Attention Deficit Hyperactivity Disorder
ASD / Autism Spectrum Disorders
CBCL / Child Behavior Checklist
COMT / catechol-O-methyltransferase
DNA / Deoxyribonucleic Acid
EEG / Encephalogram
MAO-A / Monoamine Oxidize-A
MDD / Major Depressive Disorder
OCD / Obsessive Compulsive Disorder
PDD / Pervasive Developmental Disorders
PLMS / Periodic Limb Movements in Sleep
PSG / Polysomnography
REM / Rapid Eye Movement


Sleep, Emotional and Behavioural Disturbances in Children and Adolescents

Introduction

Sleep disturbances in children and adolescents are common.e.g. 1;2 It is increasingly apparent that sleep disturbances are associated with both emotional (e.g. anxiety and depression) and behavioural (e.g. attention and conduct) difficulties in children and adolescents.3 Understanding more about co-occurring difficulties can facilitate understanding of the developmental progression of difficulties, aid researchers and clinicians in the early identification, prevention and treatment of difficulties as well as inform associated issues such as nosology (the classification of disorders). Given the known importance of sleep in youth,4 as well as the importance of having detailed knowledge of associations with other phenotypes, this review presents a selection of key empirical findings on the links between sleep and emotional and behavioural difficulties in children and adolescents. The review begins with a discussion of issues surrounding the definition and measurement of sleep disturbances. Concurrent links between sleep and emotional and behavioural difficulties are then described – followed by the presentation of longitudinal associations. A selection of possible mechanisms underlying associations are then described. The review ends with a description of future challenges for the field. These include the need to: 1) use multi-methods to assess sleep; 2) measure sleep in large-scale studies; 3) conduct controlled experiments to further establish the effects of sleep variations on emotional and behavioural difficulties; 4) take an interdisciplinary approach to further understand the links between sleep and associated difficulties.

Defining and measuring sleep disturbances

Perhaps the biggest challenge when assimilating literature on sleep and associated difficulties is the lack of consensus regarding how to assess and define sleep disturbances. Three issues concerning the assessment of sleep disturbances are noteworthy. First, sleep disturbances can take many forms. For example, a distinction can be drawn between dyssomnias (such as insomnia) and parasomnias (such as sleep walking). Furthermore, the classification of such disorders vary, depending on the system being followed – and sleep disturbances are classified by the Diagnostic and Statistical Manual for Mental Disorders5 and the International Classification of Sleep Disorders.6 A second issue is that even within sleep difficulties (e.g. sleeplessness) there is lack of consensus concerning what constitutes a problem.7 A final issue concerns measurement. Sleep can be measured objectively using measures such as polysomnography (PSG) and actigraphy (for a discussion of the role of actigraphy in sleep medicine, see elsewhere),8 as well as subjectively using questionnaires and sleep diaries. There are strengths and weaknesses of each approach. For example, objective measures of sleep may fail to capture the subjective sense of having a problem with sleep; whereas the use of subjective measures alone does not allow investigation of sleep stage differences. Furthermore, different techniques can yield different results. For example, one study showed that youth with depression had sleep disturbances as defined using sleep diaries but not encephalogram (EEG) measures.9 Even within methodologies (e.g. questionnaires), conclusions can differ depending on the precise procedure used. Indeed, child self-reports of sleep disturbances have been shown to yield more sleep problems as compared to parental reports of their children’s sleep2;10 although interestingly when focusing on clinical samples the situation appears reversed (with parents reporting more difficulties than children).11;12

Given a lack of consensus when defining and measuring sleep problems, studies to date have used numerous measures and definitions. Many studies have addressed a full range of ‘sleep-related problems’ rather than specific sleep disorders. This is particularly the case as a number of studies have capitalized on data already collected in large-scale (e.g. epidemiological) studies which have not assessed sleep thoroughly. This occurred partly because, up until recently, sleep appears to have been considered a secondary symptom of other problems rather than a phenotype worthy of consideration in its own right. In this review numerous conceptualizations of ‘sleep disturbances’, measured in different ways, are considered.

Concurrent Associations

Sleep and Emotional Problems

Links between sleep disturbances, anxiety and depression in adulthood are well established.5 In contrast, only relatively recently has there been a wide interest in these associations within childhood and adolescence. Within this field, as with sleep disturbances, emotional problems have been conceptualized in different ways. While some studies combine symptoms of anxiety and depression into a single variable,3;13 others distinguish between anxiety subtypes.14

Sleep and combined anxiety/ depression

Studies combining anxiety/ depression have reported associations with a range of different sleep disturbances. For example, in a non-clinical sample, trouble sleeping was associated with parent (but not teacher) reports of anxiety/depression in children when they were aged 6 years and again when they were aged 11 years.13 A further study reported that nightmares within childhood were associated with, amongst other symptoms, emotional difficulties.15 An additional study reported links between anxiety/depression and a composite measure of sleep disturbance in participants assessed between the ages of 4 and 15 years.3

Studies examining associations between sleep and anxiety/ depression have focused on different age groups. Interestingly, there is some evidence for developmental changes in the magnitude of associations over time. For example, one study found that the association between sleep and anxiety/depression was greater in the children aged 11 (odds ratio = 9.7) as compared to when they were aged 6 years (odds ratio = 4.7).13 Interestingly, an increase in the magnitude of the association between sleep disturbance and anxiety/ depression from childhood (age 4 years, correlation = .39) to adolescence (age 13-15 years, correlation = .52) was reported in a further report.3 One possible explanation for this trend is that sleep disturbances may be more common in children than adolescents3 and hence perhaps more part of ‘normal development’ and less significant/ indicative of a problem (although it is important to note that sleep difficulties in childhood have been linked to various difficulties both concurrently and longitudinally).e.g. 3

Sleep and anxiety

Further studies have focused on anxiety exclusively (rather than the combined anxiety/ depression phenotype). In one such community sample of adolescents, those with disturbing dreams had higher anxiety scores as compared to those who infrequently had such dreams.16 It is important to note that not all studies report robust associations between anxiety and sleep disturbances, and one community study of 8 year olds found that self-reported anxiety scores were higher in participants whose parents reported bedtime resistance than in those who did not, but not for the other seven aspects of sleep disturbances being studied (e.g. sleep onset delay).17

In addition to studies examining community samples, a number of reports have focused on clinical populations. One such study addressed the prevalence of sleep-related problems in youth with anxiety disorders – finding that one or more sleep-related problem was reported in 88% of these participants.18 While most studies do not differentiate between weekday and weekend sleep, this distinction was made in a sample comprising children with clinically-diagnosed anxiety and those who had never sought clinical intervention.19 Amongst interesting findings, anxious children reported going to bed later and having less sleep than non-anxious children on school nights. Furthermore, anxious children reported falling asleep more quickly and experiencing less night wakings during the night on weekends as compared to week nights.

Although most studies on the links between sleep and anxiety have focused on subjective measures of sleep (primarily using questionnaire measures), a few studies have considered objective measures. For example, a clinical study using objective measures of sleep in youth experiencing anxiety disorders20 found that when sleep was assessed using EEG, those with anxiety appeared to have poorer sleep than did those with depression and controls. For example, those with anxiety experienced more night wakings as compared to those with depression; and during the second night in the laboratory had a longer sleep latency as compared to both controls and those with depression.

A number of studies have distinguished subtypes of anxiety and one study reported links between sleep and obsessive compulsive disorder.11 A further study examined EEG sleep profiles in adolescents diagnosed with obsessive compulsive disorder (OCD).21 There were differences in sleep between matched controls and those diagnosed with OCD (e.g. the latter slept for a shorter total period and less time was spent in stage 2 sleep). Despite this finding, it is noteworthy that in a community sample, the correlation between sleep and OCD symptoms in adolescents was not significant.14

Certain types of anxiety as compared to others may be more strongly associated with sleep. Indeed, in a community sample of 8 year olds, self-reported sleep disturbances appeared to be more strongly associated with certain types of anxiety (e.g. school phobia) than others (e.g. social phobias)22 A further study reported that while in childhood, sleep difficulties were associated with all types of anxiety examined; within adolescence, sleep disturbance appeared to be associated with certain types of anxiety (generalized anxiety, panic/ agoraphobia and social anxiety) but perhaps not others (obsessive compulsive symptoms and separation anxiety).14 Clinical studies comparing different anxiety subtypes also suggest that sleep difficulties may be more strongly associated with certain disorders (e.g. generalized anxiety disorder) as compared to others (e.g. social anxiety).18;23

The issue of developmental change has been investigated with regards to the links between sleep and anxiety. One study found that in contrast to research focusing on combined anxiety/ depression, there did not appear to be a stronger association between sleep and anxiety in adolescents as compared to children.14

Sleep and depression

As with anxiety, studies focusing on ‘pure’ depression (rather than combined with anxiety) have found associations with subjective reports of sleep disturbances. Indeed, sleep complaints are common in prepubertal children and adolescents with depression (for a review, see elsewhere).24 As when considering mixed anxiety/ depression, associations may be influenced by age. For example, in a comparison of children and adolescents with major depressive disorder (MDD) hypersomnia was reported less commonly in the children (16%) as compared to the adolescents (34%).25 Furthermore, in a study mentioned previously, in contrast to the association with anxiety, the association between symptoms of sleep problems and depression appeared to be weaker in children (correlation = .26) as compared to adolescents (correlation = .58).14

In addition to subjective reports of sleep disturbance, objectively assessed sleep disturbances have also been investigated in association with depression. Studies have revealed mixed results – with many studies failing to find objective sleep differences in children and adolescents with depression as compared to controls.9;26;27 Other studies have reported objective sleep differences between youth with and without depression. For example, in one study incorporating polysomnography (PSG), 21 children showing symptoms of depression were compared with 7 controls.28 The group with symptoms of depression experienced shorter rapid eye movement (REM) sleep latency, longer sleep latency and REM sleep duration and a higher number of night-wakings. This finding of shorter REM sleep latency (often considered a biological marker of endogenous depression) has been reported in other samples of children29;30 and adolescents31 suffering depression. Overall, discrepancies between studies may be partly explained by differences in the age of participants and severity of depression symptoms (for a review, see elsewhere).32

Studies using other objective sleep assessment methods shed additional light on this topic. For example, an actigraphic study of rest-activity cycles in children with MDD found that in comparison to controls these children present damped circadian amplitude and lower light exposure and daytime activity levels.33 Such findings suggest that alternations in circadian rhythms could underlie changes in sleep architecture and overall clinical presentation in children and adolescents with depression.

Despite mixed reports, overall, it appears that associations between sleep and depression are stronger when focusing on subjective as compared to objective reports. Indeed, a study assessing both subjective and objective sleep in youth suffering MDD, found that depressed participants as compared to controls reported poorer sleep quality, claimed to experience a higher number of night awakenings, estimated that they were awake longer during the night and reported more difficulty waking.9 In contrast, sleep as assessed by EEG did not appear to be worse for depressed as compared to control participants.see also, 20 Similar findings have been reported for prepubertal children.e.g. 27